IMO four wheel drive is superior in pretty much every way. I dont think you'd see a major improvment in top speed but if you removed all components associated with the front wheel drive your acceleration would improve (less weight and rotating parts). Although I've herd of people running in to serious traction problems when just removing the dogbone that connects center to front differentials or remove the dogbones that connect from the front gearbox to the tire hubs. It would work if you converted the front hub things to a spindle type like off of a stadium truck,and remove the front gearbox and dogbones and got a majority of weight off the front tires you'd have something similar to a Stampede or sportmax that would work just fine.
Hope this helps